Episode Summary
Su Tangli moves into Prince Yu's residence, intending to use him for revenge against Yongqing Hou Fu. She offers herself and information but Prince Yu remains cautious, especially after she learns about a taboo surrounding his birth. Meanwhile, Prince Rui faces awkwardness with Yin Shujun after their drunken night; he visits her at Hualang Ge before leaving town, causing a stir. Song Qingzhao gifts a hairpin to Jian Mingshu, who accepts it reluctantly. Lu Chang gets jealous when Jian Mingshu gives charms to both him and Song. Just before the exams, Lu Chang is framed for an accident and jailed by Magistrate Jia. Jian Mingshu, supported by Song Qingzhao and others, tries to investigate and find the alleged victim, Qian Si, but faces difficulties.

Spoiler Alert
Serendipity: Episode 18 Recap & Spoilers – Things Are Heating Up!
First off, Xie Xu has put two and two together. He realizes Su Tangli isn't just mourning or laying low; she's cozied up to Prince Yu. And yeah, Xie Xu is definitely not planning on letting her get away with whatever she's scheming.
Speaking of Prince Yu, he's taken Su Tangli out of the Academy and brought her straight into his residence, the Yu Manor. Su Tangli isn't just going along for the ride, though. She's got revenge on her mind – specifically, using Prince Yu's power to avenge her father. She makes her move, using the excuse of delivering clothes to get an audience with the Prince. She lays it all out: she's ready to serve him, and her first offering? Intel or leverage against the Yongqing Hou Fu (Marquis Yongqing's Mansion).
But before she even gets to Prince Yu, Su Tangli sees a disturbing sight – a woman being dragged out, covered in blood. Yikes. This prompts her to discreetly ask around (slipping a eunuch some silver always helps, right?). She learns that the widely known story about Prince Yu's auspicious birth being a sign of good fortune? Yeah, that's apparently a major taboo topic in the manor. Keep that little nugget in mind.
Su Tangli basically offers herself to Prince Yu (wink, wink), but he's no fool and definitely suspicious. He questions why she didn't choose Prince Rui instead. Su Tangli cleverly replies that Prince Rui just stood by when her father was in trouble, proving he's unreliable. Prince Yu points out he has plenty of beautiful women vying for his attention; if Su Tangli wants to secure her place, she'll need to offer more than just looks. She's got her work cut out for her.
Meanwhile, over in Prince Rui's world, things are awkward. He finally gets to see his mother in the palace, and all she can talk about is how wonderful his wife, Yin Shujun (the Princess Consort), is. Mom is majorly hinting (okay, demanding) grandkids. Prince Rui just mumbles some agreements and gets out of there fast. He realizes he barely sees Yin Shujun lately; she seems to be constantly out early and back late. He thinks back to that very awkward morning when they woke up in the same bed after she got drunk, and figures she's actively avoiding him. Remember, she basically kicked him out the second she woke up that day! Now, needing an excuse to see her before he heads out of town for official business (preparing for the spring plowing ceremony), he decides to drop by Hualang Ge (her place of business/hangout?).
At Hualang Ge, Song Qingzhao has commissioned a beautiful hibiscus hairpin, clearly intending it for Jian Mingshu. There's a gathering happening, and suddenly Prince Rui shows up, much to Yin Shujun's shock. She tries to shoo him away, but he shamelessly sticks around. Things get even more cringey when Jian Mingshu asks Yin Shujun about her food preferences (to order more dishes), and Prince Rui grabs Yin Shujun's hand and won't let go, making everyone else blush or look away awkwardly.
After the meal, Prince Rui pulls Yin Shujun aside to apologize properly. Elsewhere, Song Qingzhao tries to get some alone time with Jian Mingshu (telling Wen'an Xian Zhu to give them space), but guess who crashes that party? Lu Chang. Oh, the tangled webs!
Adding a bit of comic relief, a customer mistakes Prince Rui for the shopkeeper at Hualang Ge and asks for a recommendation. After browsing, Rui picks out a hairpin identical to one Yin Shujun wears. Smooth? Maybe? Before he leaves town the next day, he entrusts Yin Shujun with managing the household affairs and she, softening a little perhaps, reminds him to dress warmly. Aww?
In a smaller side story, Wei Zhuo is visiting the ailing mother of a colleague. The old lady is confused and mistakes Zeng Yi (Auntie Zeng), who has been kindly looking after her, for her daughter-in-law. Wei Zhuo is very grateful for Zeng Yi's kindness.
Back to the main romance drama: Jian Mingshu gives Lu Chang a protective charm (a Xu Yuan Fu) she got from Xiangguo Temple. Lu Chang is thrilled... for about two seconds. Then he sees she also got one for Song Qingzhao. Jealousy flares! He snatches Jian Mingshu's own scented pouch, stuffs his charm inside, and declares that makes it unique. Okay, possessive much? Song Qingzhao then asks to speak to Jian Mingshu alone (Lu Chang resorts to eavesdropping outside). Song presents her with the custom-made hibiscus hairpin. Jian Mingshu, though not feeling any romantic sparks for Song, accepts it anyway, mainly because she doesn't want to upset him right before his crucial provincial exams (the Sheng Shi).
Just as the Academy breaks for the upcoming Spring Examinations (Chun Wei), disaster strikes. Lu Chang is heading home in an Academy-arranged carriage when someone suddenly throws themselves in front of it, claiming Lu Chang hit them. Before he knows it, Lu Chang is framed and thrown into jail! This whole thing reeks of Jia Fuyin (Magistrate Jia) deliberately causing trouble.
Jian Mingshu understandably panics when she hears the news, but thankfully she has support from Song Qingzhao, Yin Shujun, and Wen'an Xian Zhu. Song Qingzhao even escorts Jian Mingshu to the prison, and it's only because the guards see the insignia of the Zhenguo Gong Fu (Duke of Zhenguo's Mansion, likely connected to Song's family) that they let Jian Mingshu in.
Inside, Lu Chang confirms it was a setup, though he hasn't figured out who orchestrated it yet. He tells Jian Mingshu to find the supposed victim (a guy named Qian Si) to force Magistrate Jia to reopen the case. Of course, Jia Fuyin immediately runs off and tattles to Song Qingzhao's father, complaining that Song is getting too involved with the Lu siblings.
Trying to get to Qian Si, Jian Mingshu and her loyal companion Ying Xun disguise themselves as doctors making a house call, but they get turned away at the door.
So, Lu Chang is stuck in jail thanks to a frame-up, Su Tangli is playing a dangerous game in Prince Yu's manor, Prince Rui and Yin Shujun are navigating extreme awkwardness, and the love triangle between Jian Mingshu, Lu Chang, and Song Qingzhao just got even more complicated. Can't wait to see how they get out of this mess!